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Optical glass refers to a quality of glass suitable for the manufacture of optical systems such as optical lenses, prisms or mirrors.Unlike window glass or crystal, whose formula is adapted to the desired aesthetic effect, optical glass contains additives designed to modify certain optical or mechanical properties of the glass: refractive index, dispersion, transmittance, thermal expansion and ...
The international glass code is based on U.S. military standard MIL-G-174, and is a six-digit number specifying the glass according to its refractive index n d at the Fraunhofer d- (or D 3-) line, 589.3 nm, and its Abbe number V d also taken at that line.
ZBLAN is the most stable, and consequently the most used, fluoride glass, a subcategory of the heavy metal fluoride glass (HMFG) group. Typically its composition is 53% ZrF 4, 20% BaF 2, 4% LaF 3, 3% AlF 3 and 20% NaF. ZBLAN is not a single material but rather has a spectrum of compositions, many of which are still untried.
CR-39 is about half the weight of glass with an index of refraction only slightly lower than that of crown glass, and its high Abbe number yields low chromatic aberration, altogether making it an advantageous material for eyeglasses and sunglasses. A wide range of colors can be achieved by dyeing of the surface or the bulk of the material.
Eyewear frames around this time were mainly made of animal bones, horns and fabric; the implementation of wire frames in the 16th century further allowed glasses to be mass-produced. The 16th century also saw the earliest ancestors of pince-nez eyewear, which secured itself to the wearer through "pinching" the nose and later would become ...
Man with glasses. A woman with glasses. Glasses, also known as eyeglasses or spectacles, are vision eyewear with clear or tinted lenses mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms, known as temples or temple pieces, that rest over the ears for support.
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